Loans Receivable And Allowance For Credit Losses (Classified Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 184,495	$ 1,124,730
Year Two	1,122,186	1,450,679
Year Three	1,452,300	1,709,273
Year Four	1,622,110	904,106
Year Five	886,526	403,494
Prior Years	2,585,414	2,285,008
Revolving Line of Credit	112,322	110,969
Revolving Line of Credit Converted to Term Loan	6,335	6,449
Total Amortized Cost	7,971,688	7,994,708
One- to Four-Family Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	52,270	665,253
Year Two	668,235	1,117,986
Year Three	1,109,900	1,485,849
Year Four	1,460,130	817,322
Year Five	801,740	317,676
Prior Years	2,447,084	2,202,364
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	6,539,359	6,606,450
One- to Four-Family Segment [Member] | Originated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	4,014,490	4,033,028
One- to Four-Family Segment [Member] | Originated [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	50,552	318,569
Year Two	323,563	597,298
Year Three	599,827	874,518
Year Four	858,168	568,081
Year Five	556,619	251,773
Prior Years	1,600,122	1,398,616
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,988,851	4,008,855
One- to Four-Family Segment [Member] | Originated [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	1,883
Year Three	2,102	1,468
Year Four	1,893	767
Year Five	992	1,863
Prior Years	9,101	8,067
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	14,088	14,048
One- to Four-Family Segment [Member] | Originated [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	292
Year Two	0	155
Year Three	0	221
Year Four	691	564
Year Five	1,051	939
Prior Years	9,809	7,954
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	11,551	10,125
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	2,389,900	2,435,750
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1,718	346,084
Year Two	343,733	517,976
Year Three	505,493	607,968
Year Four	597,360	246,926
Year Five	242,658	62,744
Prior Years	685,581	643,520
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,376,543	2,425,218
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	308
Year Two	939	674
Year Three	916	1,674
Year Four	2,018	420
Year Five	420	357
Prior Years	1,203	1,133
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	5,496	4,566
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	1,562	0
Year Four	0	564
Year Five	0	0
Prior Years	6,299	5,402
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	7,861	5,966
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	134,969	137,672
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	131,789	134,464
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	131,789	134,464
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	0	0
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	3,180	3,208
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	3,180	3,208
Commercial Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	128,122	449,216
Year Two	444,429	324,330
Year Three	334,471	220,682
Year Four	159,617	85,373
Year Five	83,499	84,939
Prior Years	135,396	80,255
Revolving Line of Credit	39,934	38,251
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,325,468	1,283,046
Commercial Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	1,211,804	1,170,116
Commercial Segment [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	124,327	403,269
Year Two	398,195	301,164
Year Three	313,127	208,942
Year Four	148,827	81,478
Year Five	80,194	82,027
Prior Years	131,801	79,170
Revolving Line of Credit	11,725	10,448
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,208,196	1,166,498
Commercial Segment [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	2,483
Year Two	2,473	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	2,473	2,483
Commercial Segment [Member] | Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	67
Year Two	67	0
Year Three	0	0
Year Four	0	594
Year Five	594	219
Prior Years	474	255
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	1,135	1,135
Commercial Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	113,664	112,930
Commercial Segment [Member] | Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3,795	30,206
Year Two	31,101	23,166
Year Three	21,344	11,740
Year Four	10,790	3,228
Year Five	2,711	2,693
Prior Years	3,039	748
Revolving Line of Credit	28,209	27,104
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	100,989	98,885
Commercial Segment [Member] | Commercial and Industrial [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	13,191
Year Two	12,593	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	699
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	12,593	13,890
Commercial Segment [Member] | Commercial and Industrial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	73
Year Five	0	0
Prior Years	82	82
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	82	155
Consumer Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,103	10,261
Year Two	9,522	8,363
Year Three	7,929	2,742
Year Four	2,363	1,411
Year Five	1,287	879
Prior Years	2,934	2,389
Revolving Line of Credit	72,388	72,718
Revolving Line of Credit Converted to Term Loan	6,335	6,449
Total Amortized Cost	106,861	105,212
Consumer Segment [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	97,191	95,955
Consumer Segment [Member] | Home Equity [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,552	5,501
Year Two	5,341	5,624
Year Three	5,444	1,955
Year Four	1,723	1,069
Year Five	1,031	746
Prior Years	2,724	2,224
Revolving Line of Credit	71,875	72,119
Revolving Line of Credit Converted to Term Loan	5,995	6,205
Total Amortized Cost	96,685	95,443
Consumer Segment [Member] | Home Equity [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	46
Year Three	46	0
Year Four	0	0
Year Five	0	0
Prior Years	16	21
Revolving Line of Credit	43	62
Revolving Line of Credit Converted to Term Loan	226	195
Total Amortized Cost	331	324
Consumer Segment [Member] | Home Equity [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	3	15
Revolving Line of Credit	58	125
Revolving Line of Credit Converted to Term Loan	114	48
Total Amortized Cost	175	188
Consumer Segment [Member] | Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Amortized Cost	9,670	9,257
Consumer Segment [Member] | Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1,551	4,758
Year Two	4,181	2,693
Year Three	2,439	787
Year Four	640	338
Year Five	253	133
Prior Years	191	129
Revolving Line of Credit	412	412
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	9,667	9,250
Consumer Segment [Member] | Other [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	4
Year Five	3	0
Prior Years	0	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	1
Total Amortized Cost	3	5
Consumer Segment [Member] | Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	2
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior Years	0	0
Revolving Line of Credit	0	0
Revolving Line of Credit Converted to Term Loan	0	0
Total Amortized Cost	$ 0	$ 2